On article 082, do you know the relative energy of BuLi? i.e. using 3-21G
does it come between your cyclic and acyclic organolithiums?
As long as the two tetraalkyltin compounds (from stannate breakdown to
BuLi) and the two stannates are of approximately equal energy, then it does
look like your hypothesis 2 is correct (i.e. the cyclic organolithium must
be thermodynamically more stable than the acyclic organolithium, although
the energy difference from your calculations is small). If in both cases
the Li coordinates to the nitrogen lone pair then there is less
conformational freedom in the acyclic organolithium and the methyl group
(fig 4) may interact sterically with the substituents on the nitrogen atom.